[linux-2.6-block.git] / mm / frontswap.c

/*
 * Frontswap frontend
 *
 * This code provides the generic "frontend" layer to call a matching
 * "backend" driver implementation of frontswap.  See
 * Documentation/vm/frontswap.txt for more information.
 *
 * Copyright (C) 2009-2012 Oracle Corp.  All rights reserved.
 * Author: Dan Magenheimer
 *
 * This work is licensed under the terms of the GNU GPL, version 2.
 */

#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/proc_fs.h>
#include <linux/security.h>
#include <linux/capability.h>
#include <linux/module.h>
#include <linux/uaccess.h>
#include <linux/debugfs.h>
#include <linux/frontswap.h>
#include <linux/swapfile.h>

/*
 * frontswap_ops is set by frontswap_register_ops to contain the pointers
 * to the frontswap "backend" implementation functions.
 */
static struct frontswap_ops frontswap_ops __read_mostly;

/*
 * This global enablement flag reduces overhead on systems where frontswap_ops
 * has not been registered, so is preferred to the slower alternative: a
 * function call that checks a non-global.
 */
bool frontswap_enabled __read_mostly;
EXPORT_SYMBOL(frontswap_enabled);

/*
 * If enabled, frontswap_store will return failure even on success.  As
 * a result, the swap subsystem will always write the page to swap, in
 * effect converting frontswap into a writethrough cache.  In this mode,
 * there is no direct reduction in swap writes, but a frontswap backend
 * can unilaterally "reclaim" any pages in use with no data loss, thus
 * providing increases control over maximum memory usage due to frontswap.
 */
static bool frontswap_writethrough_enabled __read_mostly;

#ifdef CONFIG_DEBUG_FS
/*
 * Counters available via /sys/kernel/debug/frontswap (if debugfs is
 * properly configured).  These are for information only so are not protected
 * against increment races.
 */
static u64 frontswap_loads;
static u64 frontswap_succ_stores;
static u64 frontswap_failed_stores;
static u64 frontswap_invalidates;

static inline void inc_frontswap_loads(void) {
	frontswap_loads++;
}
static inline void inc_frontswap_succ_stores(void) {
	frontswap_succ_stores++;
}
static inline void inc_frontswap_failed_stores(void) {
	frontswap_failed_stores++;
}
static inline void inc_frontswap_invalidates(void) {
	frontswap_invalidates++;
}
#else
static inline void inc_frontswap_loads(void) { }
static inline void inc_frontswap_succ_stores(void) { }
static inline void inc_frontswap_failed_stores(void) { }
static inline void inc_frontswap_invalidates(void) { }
#endif
/*
 * Register operations for frontswap, returning previous thus allowing
 * detection of multiple backends and possible nesting.
 */
struct frontswap_ops frontswap_register_ops(struct frontswap_ops *ops)
{
	struct frontswap_ops old = frontswap_ops;

	frontswap_ops = *ops;
	frontswap_enabled = true;
	return old;
}
EXPORT_SYMBOL(frontswap_register_ops);

/*
 * Enable/disable frontswap writethrough (see above).
 */
void frontswap_writethrough(bool enable)
{
	frontswap_writethrough_enabled = enable;
}
EXPORT_SYMBOL(frontswap_writethrough);

/*
 * Called when a swap device is swapon'd.
 */
void __frontswap_init(unsigned type)
{
	struct swap_info_struct *sis = swap_info[type];

	BUG_ON(sis == NULL);
	if (sis->frontswap_map == NULL)
		return;
	frontswap_ops.init(type);
}
EXPORT_SYMBOL(__frontswap_init);

/*
 * "Store" data from a page to frontswap and associate it with the page's
 * swaptype and offset.  Page must be locked and in the swap cache.
 * If frontswap already contains a page with matching swaptype and
 * offset, the frontswap implmentation may either overwrite the data and
 * return success or invalidate the page from frontswap and return failure.
 */
int __frontswap_store(struct page *page)
{
	int ret = -1, dup = 0;
	swp_entry_t entry = { .val = page_private(page), };
	int type = swp_type(entry);
	struct swap_info_struct *sis = swap_info[type];
	pgoff_t offset = swp_offset(entry);

	BUG_ON(!PageLocked(page));
	BUG_ON(sis == NULL);
	if (frontswap_test(sis, offset))
		dup = 1;
	ret = frontswap_ops.store(type, offset, page);
	if (ret == 0) {
		frontswap_set(sis, offset);
		inc_frontswap_succ_stores();
		if (!dup)
			atomic_inc(&sis->frontswap_pages);
	} else {
		/*
		  failed dup always results in automatic invalidate of
		  the (older) page from frontswap
		 */
		inc_frontswap_failed_stores();
		if (dup) {
			frontswap_clear(sis, offset);
			atomic_dec(&sis->frontswap_pages);
		}
	}
	if (frontswap_writethrough_enabled)
		/* report failure so swap also writes to swap device */
		ret = -1;
	return ret;
}
EXPORT_SYMBOL(__frontswap_store);

/*
 * "Get" data from frontswap associated with swaptype and offset that were
 * specified when the data was put to frontswap and use it to fill the
 * specified page with data. Page must be locked and in the swap cache.
 */
int __frontswap_load(struct page *page)
{
	int ret = -1;
	swp_entry_t entry = { .val = page_private(page), };
	int type = swp_type(entry);
	struct swap_info_struct *sis = swap_info[type];
	pgoff_t offset = swp_offset(entry);

	BUG_ON(!PageLocked(page));
	BUG_ON(sis == NULL);
	if (frontswap_test(sis, offset))
		ret = frontswap_ops.load(type, offset, page);
	if (ret == 0)
		inc_frontswap_loads();
	return ret;
}
EXPORT_SYMBOL(__frontswap_load);

/*
 * Invalidate any data from frontswap associated with the specified swaptype
 * and offset so that a subsequent "get" will fail.
 */
void __frontswap_invalidate_page(unsigned type, pgoff_t offset)
{
	struct swap_info_struct *sis = swap_info[type];

	BUG_ON(sis == NULL);
	if (frontswap_test(sis, offset)) {
		frontswap_ops.invalidate_page(type, offset);
		atomic_dec(&sis->frontswap_pages);
		frontswap_clear(sis, offset);
		inc_frontswap_invalidates();
	}
}
EXPORT_SYMBOL(__frontswap_invalidate_page);

/*
 * Invalidate all data from frontswap associated with all offsets for the
 * specified swaptype.
 */
void __frontswap_invalidate_area(unsigned type)
{
	struct swap_info_struct *sis = swap_info[type];

	BUG_ON(sis == NULL);
	if (sis->frontswap_map == NULL)
		return;
	frontswap_ops.invalidate_area(type);
	atomic_set(&sis->frontswap_pages, 0);
	memset(sis->frontswap_map, 0, sis->max / sizeof(long));
}
EXPORT_SYMBOL(__frontswap_invalidate_area);

static unsigned long __frontswap_curr_pages(void)
{
	int type;
	unsigned long totalpages = 0;
	struct swap_info_struct *si = NULL;

	assert_spin_locked(&swap_lock);
	for (type = swap_list.head; type >= 0; type = si->next) {
		si = swap_info[type];
		totalpages += atomic_read(&si->frontswap_pages);
	}
	return totalpages;
}

static int __frontswap_unuse_pages(unsigned long total, unsigned long *unused,
					int *swapid)
{
	int ret = -EINVAL;
	struct swap_info_struct *si = NULL;
	int si_frontswap_pages;
	unsigned long total_pages_to_unuse = total;
	unsigned long pages = 0, pages_to_unuse = 0;
	int type;

	assert_spin_locked(&swap_lock);
	for (type = swap_list.head; type >= 0; type = si->next) {
		si = swap_info[type];
		si_frontswap_pages = atomic_read(&si->frontswap_pages);
		if (total_pages_to_unuse < si_frontswap_pages) {
			pages = pages_to_unuse = total_pages_to_unuse;
		} else {
			pages = si_frontswap_pages;
			pages_to_unuse = 0; /* unuse all */
		}
		/* ensure there is enough RAM to fetch pages from frontswap */
		if (security_vm_enough_memory_mm(current->mm, pages)) {
			ret = -ENOMEM;
			continue;
		}
		vm_unacct_memory(pages);
		*unused = pages_to_unuse;
		*swapid = type;
		ret = 0;
		break;
	}

	return ret;
}

static int __frontswap_shrink(unsigned long target_pages,
				unsigned long *pages_to_unuse,
				int *type)
{
	unsigned long total_pages = 0, total_pages_to_unuse;

	assert_spin_locked(&swap_lock);

	total_pages = __frontswap_curr_pages();
	if (total_pages <= target_pages) {
		/* Nothing to do */
		*pages_to_unuse = 0;
		return 0;
	}
	total_pages_to_unuse = total_pages - target_pages;
	return __frontswap_unuse_pages(total_pages_to_unuse, pages_to_unuse, type);
}

/*
 * Frontswap, like a true swap device, may unnecessarily retain pages
 * under certain circumstances; "shrink" frontswap is essentially a
 * "partial swapoff" and works by calling try_to_unuse to attempt to
 * unuse enough frontswap pages to attempt to -- subject to memory
 * constraints -- reduce the number of pages in frontswap to the
 * number given in the parameter target_pages.
 */
void frontswap_shrink(unsigned long target_pages)
{
	unsigned long pages_to_unuse = 0;
	int type, ret;

	/*
	 * we don't want to hold swap_lock while doing a very
	 * lengthy try_to_unuse, but swap_list may change
	 * so restart scan from swap_list.head each time
	 */
	spin_lock(&swap_lock);
	ret = __frontswap_shrink(target_pages, &pages_to_unuse, &type);
	spin_unlock(&swap_lock);
	if (ret == 0 && pages_to_unuse)
		try_to_unuse(type, true, pages_to_unuse);
	return;
}
EXPORT_SYMBOL(frontswap_shrink);

/*
 * Count and return the number of frontswap pages across all
 * swap devices.  This is exported so that backend drivers can
 * determine current usage without reading debugfs.
 */
unsigned long frontswap_curr_pages(void)
{
	unsigned long totalpages = 0;

	spin_lock(&swap_lock);
	totalpages = __frontswap_curr_pages();
	spin_unlock(&swap_lock);

	return totalpages;
}
EXPORT_SYMBOL(frontswap_curr_pages);

static int __init init_frontswap(void)
{
#ifdef CONFIG_DEBUG_FS
	struct dentry *root = debugfs_create_dir("frontswap", NULL);
	if (root == NULL)
		return -ENXIO;
	debugfs_create_u64("loads", S_IRUGO, root, &frontswap_loads);
	debugfs_create_u64("succ_stores", S_IRUGO, root, &frontswap_succ_stores);
	debugfs_create_u64("failed_stores", S_IRUGO, root,
				&frontswap_failed_stores);
	debugfs_create_u64("invalidates", S_IRUGO,
				root, &frontswap_invalidates);
#endif
	return 0;
}

module_init(init_frontswap);
Commit	Line	Data
29f233cf DM	1	/*
	2	* Frontswap frontend
	3	*
	4	* This code provides the generic "frontend" layer to call a matching
	5	* "backend" driver implementation of frontswap. See
	6	* Documentation/vm/frontswap.txt for more information.
	7	*
	8	* Copyright (C) 2009-2012 Oracle Corp. All rights reserved.
	9	* Author: Dan Magenheimer
	10	*
	11	* This work is licensed under the terms of the GNU GPL, version 2.
	12	*/
	13
	14	#include <linux/mm.h>
	15	#include <linux/mman.h>
	16	#include <linux/swap.h>
	17	#include <linux/swapops.h>
	18	#include <linux/proc_fs.h>
	19	#include <linux/security.h>
	20	#include <linux/capability.h>
	21	#include <linux/module.h>
	22	#include <linux/uaccess.h>
	23	#include <linux/debugfs.h>
	24	#include <linux/frontswap.h>
	25	#include <linux/swapfile.h>
	26
	27	/*
	28	* frontswap_ops is set by frontswap_register_ops to contain the pointers
	29	* to the frontswap "backend" implementation functions.
	30	*/
	31	static struct frontswap_ops frontswap_ops __read_mostly;
	32
	33	/*
	34	* This global enablement flag reduces overhead on systems where frontswap_ops
	35	* has not been registered, so is preferred to the slower alternative: a
	36	* function call that checks a non-global.
	37	*/
	38	bool frontswap_enabled __read_mostly;
	39	EXPORT_SYMBOL(frontswap_enabled);
	40
	41	/*
165c8aed	42	* If enabled, frontswap_store will return failure even on success. As
29f233cf DM	43	* a result, the swap subsystem will always write the page to swap, in
	44	* effect converting frontswap into a writethrough cache. In this mode,
	45	* there is no direct reduction in swap writes, but a frontswap backend
	46	* can unilaterally "reclaim" any pages in use with no data loss, thus
	47	* providing increases control over maximum memory usage due to frontswap.
	48	*/
	49	static bool frontswap_writethrough_enabled __read_mostly;
	50
	51	#ifdef CONFIG_DEBUG_FS
	52	/*
	53	* Counters available via /sys/kernel/debug/frontswap (if debugfs is
	54	* properly configured). These are for information only so are not protected
	55	* against increment races.
	56	*/
165c8aed KRW	57	static u64 frontswap_loads;
	58	static u64 frontswap_succ_stores;
	59	static u64 frontswap_failed_stores;
29f233cf DM	60	static u64 frontswap_invalidates;
29f233cf DM	61
165c8aed KRW	62	static inline void inc_frontswap_loads(void) {
165c8aed KRW	63	frontswap_loads++;
29f233cf	64	}
165c8aed KRW	65	static inline void inc_frontswap_succ_stores(void) {
165c8aed KRW	66	frontswap_succ_stores++;
29f233cf	67	}
165c8aed KRW	68	static inline void inc_frontswap_failed_stores(void) {
165c8aed KRW	69	frontswap_failed_stores++;
29f233cf DM	70	}
	71	static inline void inc_frontswap_invalidates(void) {
	72	frontswap_invalidates++;
	73	}
	74	#else
165c8aed KRW	75	static inline void inc_frontswap_loads(void) { }
	76	static inline void inc_frontswap_succ_stores(void) { }
	77	static inline void inc_frontswap_failed_stores(void) { }
29f233cf DM	78	static inline void inc_frontswap_invalidates(void) { }
	79	#endif
	80	/*
	81	* Register operations for frontswap, returning previous thus allowing
	82	* detection of multiple backends and possible nesting.
	83	*/
	84	struct frontswap_ops frontswap_register_ops(struct frontswap_ops *ops)
	85	{
	86	struct frontswap_ops old = frontswap_ops;
	87
	88	frontswap_ops = *ops;
	89	frontswap_enabled = true;
	90	return old;
	91	}
	92	EXPORT_SYMBOL(frontswap_register_ops);
	93
	94	/*
	95	* Enable/disable frontswap writethrough (see above).
	96	*/
	97	void frontswap_writethrough(bool enable)
	98	{
	99	frontswap_writethrough_enabled = enable;
	100	}
	101	EXPORT_SYMBOL(frontswap_writethrough);
	102
	103	/*
	104	* Called when a swap device is swapon'd.
	105	*/
	106	void __frontswap_init(unsigned type)
	107	{
	108	struct swap_info_struct *sis = swap_info[type];
	109
	110	BUG_ON(sis == NULL);
	111	if (sis->frontswap_map == NULL)
	112	return;
f9f08103	113	frontswap_ops.init(type);
29f233cf DM	114	}
	115	EXPORT_SYMBOL(__frontswap_init);
	116
	117	/*
165c8aed	118	* "Store" data from a page to frontswap and associate it with the page's
29f233cf DM	119	* swaptype and offset. Page must be locked and in the swap cache.
	120	* If frontswap already contains a page with matching swaptype and
	121	* offset, the frontswap implmentation may either overwrite the data and
	122	* return success or invalidate the page from frontswap and return failure.
	123	*/
165c8aed	124	int __frontswap_store(struct page *page)
29f233cf DM	125	{
	126	int ret = -1, dup = 0;
	127	swp_entry_t entry = { .val = page_private(page), };
	128	int type = swp_type(entry);
	129	struct swap_info_struct *sis = swap_info[type];
	130	pgoff_t offset = swp_offset(entry);
	131
	132	BUG_ON(!PageLocked(page));
	133	BUG_ON(sis == NULL);
	134	if (frontswap_test(sis, offset))
	135	dup = 1;
ef383597	136	ret = frontswap_ops.store(type, offset, page);
29f233cf DM	137	if (ret == 0) {
29f233cf DM	138	frontswap_set(sis, offset);
165c8aed	139	inc_frontswap_succ_stores();
29f233cf DM	140	if (!dup)
29f233cf DM	141	atomic_inc(&sis->frontswap_pages);
d9674dda	142	} else {
29f233cf DM	143	/*
	144	failed dup always results in automatic invalidate of
	145	the (older) page from frontswap
	146	*/
165c8aed	147	inc_frontswap_failed_stores();
d9674dda SL	148	if (dup) {
	149	frontswap_clear(sis, offset);
	150	atomic_dec(&sis->frontswap_pages);
	151	}
4bb3e31e	152	}
29f233cf DM	153	if (frontswap_writethrough_enabled)
	154	/* report failure so swap also writes to swap device */
	155	ret = -1;
	156	return ret;
	157	}
165c8aed	158	EXPORT_SYMBOL(__frontswap_store);
29f233cf DM	159
	160	/*
	161	* "Get" data from frontswap associated with swaptype and offset that were
	162	* specified when the data was put to frontswap and use it to fill the
	163	* specified page with data. Page must be locked and in the swap cache.
	164	*/
165c8aed	165	int __frontswap_load(struct page *page)
29f233cf DM	166	{
	167	int ret = -1;
	168	swp_entry_t entry = { .val = page_private(page), };
	169	int type = swp_type(entry);
	170	struct swap_info_struct *sis = swap_info[type];
	171	pgoff_t offset = swp_offset(entry);
	172
	173	BUG_ON(!PageLocked(page));
	174	BUG_ON(sis == NULL);
	175	if (frontswap_test(sis, offset))
ef383597	176	ret = frontswap_ops.load(type, offset, page);
29f233cf	177	if (ret == 0)
165c8aed	178	inc_frontswap_loads();
29f233cf DM	179	return ret;
29f233cf DM	180	}
165c8aed	181	EXPORT_SYMBOL(__frontswap_load);
29f233cf DM	182
	183	/*
	184	* Invalidate any data from frontswap associated with the specified swaptype
	185	* and offset so that a subsequent "get" will fail.
	186	*/
	187	void __frontswap_invalidate_page(unsigned type, pgoff_t offset)
	188	{
	189	struct swap_info_struct *sis = swap_info[type];
	190
	191	BUG_ON(sis == NULL);
	192	if (frontswap_test(sis, offset)) {
ef383597	193	frontswap_ops.invalidate_page(type, offset);
29f233cf DM	194	atomic_dec(&sis->frontswap_pages);
	195	frontswap_clear(sis, offset);
	196	inc_frontswap_invalidates();
	197	}
	198	}
	199	EXPORT_SYMBOL(__frontswap_invalidate_page);
	200
	201	/*
	202	* Invalidate all data from frontswap associated with all offsets for the
	203	* specified swaptype.
	204	*/
	205	void __frontswap_invalidate_area(unsigned type)
	206	{
	207	struct swap_info_struct *sis = swap_info[type];
	208
	209	BUG_ON(sis == NULL);
	210	if (sis->frontswap_map == NULL)
	211	return;
ef383597	212	frontswap_ops.invalidate_area(type);
29f233cf DM	213	atomic_set(&sis->frontswap_pages, 0);
	214	memset(sis->frontswap_map, 0, sis->max / sizeof(long));
	215	}
	216	EXPORT_SYMBOL(__frontswap_invalidate_area);
	217
96253444 SL	218	static unsigned long __frontswap_curr_pages(void)
	219	{
	220	int type;
	221	unsigned long totalpages = 0;
	222	struct swap_info_struct *si = NULL;
	223
	224	assert_spin_locked(&swap_lock);
	225	for (type = swap_list.head; type >= 0; type = si->next) {
	226	si = swap_info[type];
	227	totalpages += atomic_read(&si->frontswap_pages);
	228	}
	229	return totalpages;
	230	}
	231
f116695a SL	232	static int __frontswap_unuse_pages(unsigned long total, unsigned long *unused,
	233	int *swapid)
	234	{
	235	int ret = -EINVAL;
	236	struct swap_info_struct *si = NULL;
	237	int si_frontswap_pages;
	238	unsigned long total_pages_to_unuse = total;
	239	unsigned long pages = 0, pages_to_unuse = 0;
	240	int type;
	241
	242	assert_spin_locked(&swap_lock);
	243	for (type = swap_list.head; type >= 0; type = si->next) {
	244	si = swap_info[type];
	245	si_frontswap_pages = atomic_read(&si->frontswap_pages);
	246	if (total_pages_to_unuse < si_frontswap_pages) {
	247	pages = pages_to_unuse = total_pages_to_unuse;
	248	} else {
	249	pages = si_frontswap_pages;
	250	pages_to_unuse = 0; /* unuse all */
	251	}
	252	/* ensure there is enough RAM to fetch pages from frontswap */
	253	if (security_vm_enough_memory_mm(current->mm, pages)) {
	254	ret = -ENOMEM;
	255	continue;
	256	}
	257	vm_unacct_memory(pages);
	258	*unused = pages_to_unuse;
	259	*swapid = type;
	260	ret = 0;
	261	break;
	262	}
	263
	264	return ret;
	265	}
	266
69217b4c SL	267	static int __frontswap_shrink(unsigned long target_pages,
	268	unsigned long *pages_to_unuse,
	269	int *type)
	270	{
	271	unsigned long total_pages = 0, total_pages_to_unuse;
	272
	273	assert_spin_locked(&swap_lock);
	274
	275	total_pages = __frontswap_curr_pages();
	276	if (total_pages <= target_pages) {
	277	/* Nothing to do */
	278	*pages_to_unuse = 0;
	279	return 0;
	280	}
	281	total_pages_to_unuse = total_pages - target_pages;
	282	return __frontswap_unuse_pages(total_pages_to_unuse, pages_to_unuse, type);
	283	}
	284
29f233cf DM	285	/*
	286	* Frontswap, like a true swap device, may unnecessarily retain pages
	287	* under certain circumstances; "shrink" frontswap is essentially a
	288	* "partial swapoff" and works by calling try_to_unuse to attempt to
	289	* unuse enough frontswap pages to attempt to -- subject to memory
	290	* constraints -- reduce the number of pages in frontswap to the
	291	* number given in the parameter target_pages.
	292	*/
	293	void frontswap_shrink(unsigned long target_pages)
	294	{
f116695a SL	295	unsigned long pages_to_unuse = 0;
f116695a SL	296	int type, ret;
29f233cf DM	297
	298	/*
	299	* we don't want to hold swap_lock while doing a very
	300	* lengthy try_to_unuse, but swap_list may change
	301	* so restart scan from swap_list.head each time
	302	*/
	303	spin_lock(&swap_lock);
69217b4c	304	ret = __frontswap_shrink(target_pages, &pages_to_unuse, &type);
29f233cf	305	spin_unlock(&swap_lock);
69217b4c SL	306	if (ret == 0 && pages_to_unuse)
69217b4c SL	307	try_to_unuse(type, true, pages_to_unuse);
29f233cf DM	308	return;
	309	}
	310	EXPORT_SYMBOL(frontswap_shrink);
	311
	312	/*
	313	* Count and return the number of frontswap pages across all
	314	* swap devices. This is exported so that backend drivers can
	315	* determine current usage without reading debugfs.
	316	*/
	317	unsigned long frontswap_curr_pages(void)
	318	{
29f233cf	319	unsigned long totalpages = 0;
29f233cf DM	320
29f233cf DM	321	spin_lock(&swap_lock);
96253444	322	totalpages = __frontswap_curr_pages();
29f233cf	323	spin_unlock(&swap_lock);
96253444	324
29f233cf DM	325	return totalpages;
	326	}
	327	EXPORT_SYMBOL(frontswap_curr_pages);
	328
	329	static int __init init_frontswap(void)
	330	{
	331	#ifdef CONFIG_DEBUG_FS
	332	struct dentry *root = debugfs_create_dir("frontswap", NULL);
	333	if (root == NULL)
	334	return -ENXIO;
165c8aed KRW	335	debugfs_create_u64("loads", S_IRUGO, root, &frontswap_loads);
	336	debugfs_create_u64("succ_stores", S_IRUGO, root, &frontswap_succ_stores);
	337	debugfs_create_u64("failed_stores", S_IRUGO, root,
	338	&frontswap_failed_stores);
29f233cf DM	339	debugfs_create_u64("invalidates", S_IRUGO,
	340	root, &frontswap_invalidates);
	341	#endif
	342	return 0;
	343	}
	344
	345	module_init(init_frontswap);